Gas turbines include components, such as buckets (blades), nozzles (vanes), combustors, shrouds, and other hot gas path components which are coated with a thermal barrier coating to protect the components from the extreme temperatures, chemical environments and physical conditions found within the gas turbines. A bond coating may be applied between the component and the thermal barrier coating, said bond coating increasing the bond strength of the thermal barrier coating to the component and offering additional protection. Such bond coatings are often applied during the manufacturing process of the gas turbine component.
However, many gas turbine components are modified at some point during their life cycle. For example, some components are modified to adjust shape and/or geometry prior to being placed in service. Other components may be modified after having been placed in service to replace materials and/or change the geometry of the component. In many instances, this modification of the components includes joining or adding material, which is usually preceded by the removal of the bond coating and/or thermal barrier coating and then followed by re-coating.
The removing and re-coating of the bond coating and/or thermal barrier coating, such as, for example, through stripping with an acid, extends the duration of the modification period for the component. Additionally, the stripping and re-coating increases the cost of modification, typically accounting for more than 30 to 40% of the modification cost. Thus, there would be considerable cost and time saving potential in avoiding stripping and re-coating.